How to derive a relative path using Ant

Question

I'm using Ant and mxmlc to compile ActionScript classes and MXML into swfs, while maintaining the default organization of a Flex Builder (Flash Builder) project. Many of my ActionScript classes are in project subdirectories, so my project is organized like the following:

MyBigProject
-build-imports.xml
-build.xml

-bin-debug
--src
---flash
---app
----CoolWidget1.swf
---Main.swf
--test

-src
--flash
---app
----build-imports.xml
----build.xml
----CoolWidget1.as
--build-imports.xml
--build.xml
--Main.mxml
-test

This directory structure maintains the default directory structure of a Flash Builder project so I can perform push-button builds from the Flash Builder IDE. I've added the Ant build xml's to this project so I can also build from the command line. I'm trying to create portable ant build scripts that require the least changes to reuse in other projects. I have everything like I want except for deriving relative paths.

The build-imports.xml file at the root of the project contains the following:

<project name="project.root.imports">
    <dirname property="project.root.dir" file="${ant.file.project.root.imports}"/>
</project>

While the sub project folders contain build-imports.xml with the following:

<project name="MyBigProject.src.flash.app.imports">
    <import file="../build-imports.xml" />
</project>

Notice that sub project build-imports.xml walks up the directory hiearchy till it gets to the root build-imports.xml, and there I set the project.root.dir.

I can then use the ${project.root.dir}/bin-debug to specify where to place my binaries. The only problem I have, is I do not know how to create the same directory structure as what lies under my src folder. I need to be able to derive a relative path or perform some string manipulation to create new directorys.

Considering the above information, how do I take a known path like:
${project.root.dir}/src/app
and derive a directory path like:
${project.root.dir}/bin-debug/app

I've found some information about the Ant-contribu propertyregex task, which would allow some string manipulation, but I'm hoping there is an Ant guru out there that can point to a simple solution. I believe it's highly likely as an Ant novice, I'm simply overlooking the obvious.

Answer 1

My build files have evolved a bit since I posted, but I've resolved the problem. I believe the following would work correctly in the basic setup previously described:

Add this to the default target in the sub project's build.xml

<path id="build.path">
   <pathelement location="." />
</path>
<pathconvert property="build.dir" refid="build.path">
    <map from="${project.root.dir}" to="${project.root.dir}/bin-debug"/>
</pathconvert>